1. Field of the Invention
The present invention relates to a photoelectric conversion device for photoelectrically converting light incident through an optical system such as a lens, and an image pickup device and autofocus camera using the same, including, e.g., the optical system.
2. Related Background Art
A conventional photoelectric conversion device having two-dimensionally arrayed photoelectric conversion elements has an arrangement shown in FIG. 1. Referring to FIG. 1, the device comprises pixels 1 as photoelectric conversion elements, output lines 2, light-shielding films 3, aperture regions 4, a scanning circuit 5, and a signal transfer circuit 6. The pixels 1 are two-dimensionally arrayed at a predetermined pitch. Each aperture 4 has the same shape and same area as those of the corresponding pixel 1 and is formed at the same position as that of the pixel 1.
The scanning circuit 5 scans the two-dimensionally arrayed pixels 1 in the horizontal and vertical directions and outputs signals to the signal transfer circuit 6.
In the conventional photoelectric conversion device, two-dimensionally photoelectrically converted signals are time-serially output from the signal transfer circuit 6, processed in accordance with a standard such as NTSC or HDTV, and output to an external device. After this, the signals are processed by an external signal processing circuit and reproduced on a TV or monitor. In this case, the image formed on the photoelectric conversion device can be reproduced on a TV monitor in a one-to-one correspondence. Unless the image pickup lens has any aberrations, an accurate image can be reproduced.
In the prior art, however, when the optical system has aberrations, and this device is used for the autofocus (AF) sensor of a camera, the following problems are posed.
As an AF light beam, the light image of an object to be photographed is input. The light beam is focused by an objective lens and then sent to the photoelectric conversion device while changing the direction of the beam by a plurality of reflection mirrors, thereby focusing the objective lens on the object. In the process in which the light beam is reflected by each reflection mirror and focused, it is distorted due to aberrations of the mirrors and objective lens. For example, when the object to be photographed has a rectangular pattern, the light beam is curved and focused on the photoelectric conversion device as an AF sensor. This distortion is conventionally corrected using an image signal processing circuit inserted after the signal transfer circuit, or by signal processing software. However, the correction is insufficient.
When an image is reproduced through the conventional sensor, an image to be reproduced in a rectangular shape curves. This results in disadvantages in subsequent signal processing and makes it difficult to perform accurate AF operation.
It is the first object of the present invention to correct, on a photoelectric conversion device, aberration generated in the optical system of an image pickup device.
It is the second object of the present invention to correct, on a photoelectric conversion device, light amount nonuniformity in an optical system, such as a decrease in marginal light amount of a lens.
In order to achieve the above object, according to an aspect of the present invention, an aperture position of each photoelectric conversion element differs from that of an adjacent aperture position in a photoelectric conversion region in correspondence with aberration in an optical system of an actually used image pickup device. According to another aspect of the present invention, an aperture ratio of an aperture region of each photoelectric conversion element is changed in units of arrangement positions in a photoelectric conversion region in correspondence with an amount of light focused on a photoelectric conversion device.
In the above arrangement, since each aperture of the photoelectric conversion device is arranged in correspondence with actual aberration in the optical system, aberration of an image due to the optical system is corrected on the photoelectric conversion device. In addition, by setting the aperture ratio of each aperture in correspondence with the light amount in the optical system, the same output level can be obtained in irradiating light in the same amount.